Global problems related to biodiversity
science,
especially the effects of invasive species

José SarukhanChair, Diversitas; UNAM, Mexico

Public awareness about the accelerated loss of species at both the
local and global scales has increased in the last decade, and has crystallised in
international consensus about the relevance of the subject. The most important such
consensus is represented by the Convention of Biodiversity (CBD), which together with the
Convention on Climate Change have become key components of the international agenda on
global environmental issues, triggered by the 1992 Rio de Janeiro meeting.

The CBD recognises clearly that the conservation of Biodiversity, as
well as the factors that threaten it, are problems that transcend economic, political,
religious and cultural frontiers (UNEP, 1992). They also transcend the merely quantitative
aspect of the loss of species belonging to many different taxonomic groups in a certain
region, which in it constitutes a very important issue. It expands both to a Global scale
problem and to a variety of factors fundamental for maintaining life as we know it, for us
and for the rest of organisms with which we share this Planet.

All those factors are linked and dependent on the biological diversity
which composes the variety of ecosystems of the world, either natural or man-made, often
in ways which make them difficult to be understood and predictable. Additionally, the
complexity of those factors is not limited to the realm of the bio-geo-physical sciences,
but includes in a very central way, intricate social issues.

Human activity is causing changes in the environment which, directly or
indirectly are causing the extinction of scores of species in both terrestrial and aquatic
systems at a rate that, if it is maintained, will represent the most severe process of
extinction in the recorded history of our planet since life developed in it. The most
serious loss, besides that of taxa, is the loss of the multiple and fundamental services,
which the ecosystems formed by the complex interactions of those species, provide to
mankind. These processes of ecosystem loss are presented and discussed.

The second most important factor in the loss of Biological diversity at
a Global scale is the accidental or purposeful introduction of exotic species which become
aggressive invasive in the new areas they are introduced, causing besides the
disappearance of populations and entire species, enormous economic hardship. The factors
involved in this process are presented and discussed.

The environmental consequences
of tropical deforestation

Carlos Cerri Universidade de São Paulo,
Brazil

At the close of the twentieth century, there are approximately
3,5000 million hectares of forest in the world. Of this total forest area, 2,000 million
hectares are found in tropical regions (FAO, 1997).

Tropical forest offers a very wide range of highly valuable services.
To illustrate, the forest serves important watershed and climate control functions,
especially in regulation of stream flows by intercepting rainfall, absorbing the water
into the underlying soil, and gradually releasing it into the streams and rivers of its
watershed. The forest absorbs albedo (reflectivity of the sun's rays) from the sun, and
stores a sizeable share of the world's carbon. Forests absorb atmospheric carbon and
replenish the oxygen in the air we breathe. The tropical forest is the most important
source of biodiversity on earth. They are the home to 70 percent of all the earth's
species (Roper & Roberts, 1999). Industrial wood products account for US$ 400 billion
worth of global production. Tropical forest account for approximately 25 percent of this
production (WCFSD, 1998). Undisturbed tropical forests furnish essential foods, clothing,
and implements for indigenous forest people.

Deforestation is the permanent loss of forest to other land uses such
as agriculture, grazing, new settlements, infrastructure, and dam reservoirs (WCFSD,
1998).

At the present time, 14 to 16 million hectares of tropical forests are
being converted to other land uses, mostly agricultural. FAO (1997) has estimated the
annual rates of deforestation in developing countries at 15.5 million hectares for the
period 1980-1990 and 13.7 million hectares for 1990-1995. The total forest area lost
during the 15-year period was approximately 200 million hectares. The tragedy lies in the
fact that most of these deforested lands are not suited for long-term farming or grazing
and they quickly degrade once the forest has been cut and burnt (Roper & Roberts,
1999).

The predisposing conditions that favour deforestation include poverty,
greed, and quest for power, population growth, and illiteracy. The indirect causes of
deforestation include inappropriate government policies, land hunger, national and global
market forces, and the undervaluation of natural forests, weak government institutions,
and social factors. The more visible direct causes of deforestation include the land uses
that compete with the natural forests (e.g. agriculture, ranching, infrastructure
development, and mining and petroleum exploration). Logging, fuelwood collection, and tree
plantations also have a role in the deforestation phenomena.

In some cases, deforestation can be beneficial. Given the right mix of
social needs, economic opportunities, and environmental conditions, it can be a rational
conversion from one type of land use to a more productive one (Roper & Roberts, 1999).

The economic and environmental consequences of deforestation are
profound, making it one of the most critical issues facing our global society. In economic
terms, the tropical forest destroyed each year represent a loss in forest capital valued
at US$ 45 billion (WCFSD, 1998). Tropical deforestation is a major component of the carbon
cycle and has profound implications for biological diversity. Deforestation increases
atmospheric CO2 and other trace gases, possibly affecting climate (Bruce ET al., 1999).
Conversion of forests to cropland and pasture results in a net flux of carbon to the
atmosphere because the concentration of carbon in forests is higher than that in the
agricultural areas that replace them. The paucity of data on tropical deforestation limits
our understanding of the carbon cycle and possible climate change (IPCC, 1998). Probably
the most serious and most short-sighted consequence of deforestation is the loss of
biodiversity. Deforestation affects biological diversity in three ways: destruction of
habitat, isolation of fragments of formerly contiguous habitat, and edge effects within a
boundary zone between forest and deforested areas. This boundary zone extends some
distance into the remaining forest. In this zone there are greater exposure to winds;
dramatic micrometeorological differences over short distances; easier access for
livestock, other nonforest animals, and hunters; and a range of other biological and
physical effects. The result is a net loss of plant and animal species in the edge areas
(Roper & roberts, 1999). The long-term impact of deforestation on the soil resource
can be severe. Clearing the vegetative cover for slash and burn farming exposes the soil
to the intensity of the tropical sun and torrential rains. This can negatively affect the
soil by increasing its compaction, reducing its organic material, leeching out its few
nutrients available, increasing its aluminium toxicity of soils, making it marginal for
farming. In many cases, political decision-makers knowingly permit deforestation to
continue because it acts as a social and economic safety valve.

While it is impossible to stop deforestation in the foreseeable future, there are many
opportunities for bringing it under control and minimising its negative impacts.
Alternatives include the protection and management of remaining forests socio-economic
development in rural areas, and policy and institutional reforms.

Water resources for human use:
a perspective in view of the climate variability impacts.

María Concepción Donoso DirectorCATHALAC, Panama

Water promises to be the
single most important issue in the coming century. It will engage development leaders,
activists and critics all in the next decades. Of all the water that exists on earth only
2.5% is not sea or salt water, of which 0,3% is available in lakes and rivers. Therefore,
as far as human use is concerned, less than 0.08 of 1 per cent of all of the water on the
planet is considered freshwater. The amount and distribution of freshwater in space and in
time, varies considerably at a global scale. Some regions experience an annual rainfall of
over 2000 mm, evenly distributed throughout the year, while others barely reach a few
millimeters. However, a vast majority of the countries suffer frequently f

rom a distinct seasonal pattern, where precipitation reaches extreme high amounts during
the wet season, serious water shortages and droughts may occur during the rest of the
year. Anomalous precipitation patterns, in the form of extremely severe drought or
excessive rainfall, are modulated by climate variability. Complex air-sea-land interaction
processes regulate climate variability at different global scales. Climate variability is
a natural phenomenon and humanity has to deal with it. The negative impact of droughts or
excess precipitation can be increased due to human activities. Anthropogenic processes put
additional stress on water resources. Overpopulation, together with extensive agriculture,
industrialization, and soil erosion due to changes in land cover, are the major
man-induced stress agents on water resources in the region. Consequently, a comprehensive
integrated water management system is extremely difficult to develop and to implement at a
global scale.

In the next century, a priority objective in Science is to acquire
better understanding of the air-sea-land interactions that dominate climate variability at
global and regional scales. The sometimes severe repercussions of these interactions
stresses the need for assessing their impacts while improving our knowledge of the complex
mechanisms that control these physical processes. One of these interactive processes is
the El Niño (also known as El Niño - Southern Oscillation, or ENSO), and its counterpart
La Niña (also known as the cold ENSO phase). The present work focuses on the effect of El
Niño and La Niña on water distribution and availability for human use, with especial
emphasis on the 1997-1998 El Niño event. and the 1998-1999 La Niña phase. Assessment is
performed on the effects of these climatic events on crucial economic sectors, such as
health, agriculture, energy, and others Water is the linking element that dominates the
activity of all these sectors. Finally, an overview of the political and social
consequences of these impacts is presented.

Global climate change and cycling of
toxic metals

Jerome Nriagu School of Public Health, University of Michigan; Nigeria

This presentation will explore the relationships between and global
climate change (GCC) and the cycling of toxic metals in the environment. Among other
things, GCC is expected to result in (a) an increase in the amount of UV-B radiation
reaching the earths surface, (b) a change (increase) in temperature of the
atmosphere and earths surface, and (c) a change in the hydrological regime,
especially the incidence of catastrophic weather incidents such as floods, storms and
droughts. These changes will link GCC to heavy metal cycle in many ways. (I) For some
metals (especially mercury), the ratio of emissions from industrial sources and natural
processes (sources) is expected to change; GCC may also change the current deposition
pattern and can result in further dispersion of already deposited toxic metals. (II) Sites
around the world are heavily contaminated with mercury (including abandoned gold and
silver mines and chlor-alkali plant graveyards) and a change in climate may lead to
increased exhalation of mercury from these so-called "chemical time bombs".
(III) Many natural and anthropogenic sources emit toxic metals in forms that can undergo
photochemical reactions in the atmosphere. For instance, the removal of mercury from the
atmosphere is driven by the formation of reactive Hg(II) species by direct and indirect
photochemical processes which are temperature-dependent. GCC can thus alter the current
deposition pattern for atmospheric mercury in many parts of the world. (IV) Global climate
change is expected to trigger an increase in rates of biogenic production and release of
volatile metal compounds, especially the methylated compounds of mercury, arsenic,
selenium and lead which are more readily taken up by the biota. (V) Increased
remobilization of previously deposited pollutant metals may convert some areas (such the
northeastern region of the United States) from being a sink to an area source of toxic
metals. (VI) Bioaccumulation of toxic metals by fish is closed linked to production of
dissolved organic carbon (DOC) and water temperature, and these habitat characteristics
are strongly influenced by GCC. (VII) Extensive flooding of coastal and low-lying areas
would exert a drastic influence on the mercury cycle by increasing the efficiency and
rates of mercury methylation as well as the levels in water, zooplankton, benthic
invertebrates and fish in the newly formed bodies of water. The downstream effects of the
flooded areas may expose a significant fraction of the rich fisheries resource of many
coastal areas to risk of mercury contamination. (VIII) In temperate lakes, changes in food
chain structure and function tend to be non-linear so that small changes due to climate
may result in rapid and drastic changes in bioaccumulation rates. (IX). Tropical and
arctic ecosystems are particularly sensitive to heavy metal pollution. Because of the
unique features of the food web, top predators of tropical and arctic ecosystems are more
vulnerable to heavy metals compared to temperate species, and global warming can further
exacerbate the exposure of the most sensitive organisms to toxic metal pollutants.

Human activities have changed the natural biogeochemical cycle of toxic
metals in many ecosystems. The presentation will show that global climate change can
increase the risk of exposure of many people to toxic metals by changing the forms as well
as the remobilization and bioaccumulation rates of this class of pollutants.

The role of the oceans in global climate change

John C. Field President, SCOR; University of Cape Town, South Africa

One of the challenges facing oceanographers at the turn of the
millennium is predicting the nature and consequences of global warming. The enormous heat
capacity of the oceans and their huge capacity to store dissolved CO2 are
important characteristics. Understanding the role of the oceans is therefore central to
predicting global change. This talk highlights a few of many factors and unknowns involved
in predicting future scenarios in the ocean. Transport of CO2 in the oceans is
strongly influenced by the physical "solubility pump" whereby the solubility of
gases such as CO2 increases in seawater as it is cooled in winter at high
latitudes. The prime site is in the Arctic North Atlantic where Atlantic Deep Water is
formed by convective sinking of the cool, denser water, taking with it newly dissolved
atmospheric CO2 .This forms the basis of the deep ocean
thermohaline circulation, which takes of the order of a thousand years to complete its
slow conveyer belt circulation through the ocean basins and back up to the surface,
sequestering CO2 from the atmosphere for many centuries. This has now been
shown to have varied strongly (possibly even reversed) between the ice-ages and
interglacial periods. The changes in this circulation pattern have not happened gradually
but suddenly, as if triggered at a threshold. This has profound implications for the
storage of the anthropogenic CO2 accumulating in the atmosphere. The biological
pump, based on sinking of organic matter produced by phytoplankton, depends on the
physical environment and the supply of nutrients to the sunlit surface ocean. Until
recently, nitrate was assumed to be the main limiting nutrient in the oceans but it has
been convincingly shown that vast areas of the Equatorial Pacific, the temperate northern
Pacific and now the Southern Ocean, are limited by the supply of trace amounts of iron,
not nitrate. It is suggested that many coastal areas, and ocean areas downwind of deserts,
are not iron limited because of the aeolian transport of iron in the dust blown off the
land and into the oceans, e.g. the North Atlantic is largely fertilized by the Sahara
Desert. Thus the activity of the biological CO2 pump may be strongly influenced
by other elements, including trace elements, in a strongly non-linear fashion, making
prediction very difficult. The situation becomes more complicated when one considers that
the composition of biological communities of organisms is strongly influenced by small
changes in their physical and chemical environment. Dimethyl sulphide (DMS) is the major
naturally-produced source of sulphur to the atmosphere. DMS produces aerosol particles
which affect the radiative properties of stratus clouds, with a strong cooling effect on
climate, thus damping global warming. DMS production in turn depends on the composition of
phytoplankton communities in surface waters, which is sensitive to their environment.
Climate models, which include aerosols, have performed better than those that do not have.

A geologic hazard is a potentially destructive agent -- a process
or an event -- whose direct interaction with the material environment could cause harm to
man and his investments. Geologic events such as earthquakes, volcanic eruptions,
landslides and tsunami are, in reality, normal earth processes that have been occuring and
recurring even before historic time. These events or processes are manifestations of
natural forces at work, indications that our Planet Earth is alive and dynamic. They have
become hazards and thus a risk to people, properties and infrastructures because people
have chosen to build settlements and structures on sites likely to be impacted by these
phenomena  on flat terrains, near the coasts, at river mouths, at the bases of
mountains, on the slopes of active volcanoes, or in areas traversed by or near active
faults.

Almost all types of geologic hazards occur in the Philippines. Just by
looking at the geologic map of the archipelago, one finds proof of the reality of these
hazards in the physical presence of their generators  active and potentially active
volcanoes, criss-crossing, active and potentially active faults, steep slopes, active
subduction zones, trenches, and others. Moreover, in view of its geographic location,
being near the equator and the edge of the Pacific Ring of Fire, the Philippines has also
been the object of some foreign-sourced geologic hazards.

The magnitude 7.8, July 16, 1990, Northern Luzon earthquake generated a
125 km long ground rupture with maximum horizontal displacement of 6.6 m and vertical
displacement of 2.0m. Strong ground shaking caused many buildings to collapse or sustain
heavy damage and triggered shallow landslides in the mountainous regions and liquefaction
in the coastal areas and fluvial environs of Central Luzon. The combined effects of
surface faulting, ground shaking, landslides, liquefaction and lateral spreading took a
toll of 1200 lives and more than P18 billion in actual damage to properties and
infrastructures and losses in agricultural and industrial production. The Pinatubo Volcano
eruption in 1999 is one of the worlds most violent and destructive eruptions of this
century. Pinatubos major eruptive episodes on 12-16 June 1991 spewed out some 7 cu
km of pyroclastic flows and about 3 cu km of ashfall. The powerfully ejected and tall
eruption plumes reached well into the stratosphere and affected global climate. The huge
volume of pyroclastic flow deposits buried and rendered uncultivable agricultural lands
and agro-forest farms. Continuous heavy rains later remobilized these ashfall and
pyroclastic flow deposits into another destructive agent - which in turn inundated, buried
and/or destroyed more agricultural lands, settlements and infrastructures. Casualties
directly attributed to the eruption are few  less than 300, but the environmental
and economic impacts are considerable and are still being felt as Pinatubo lahars continue
to plague the country.

During the last half of the 20th century human activities have
resulted in approximate doubling the rate of production of biologically available,
ìfixedî nitrogen on a global basis (Vitousek, P. et al., 1997. Ecological Applications
7: 737-750). This is the result of the increases in the manufacture of chemical
fertilizers to support the needs of agricultural production, the combustion of fossil
fuels that released fixed-nitrogen into the atmosphere, the planting of nitrogen-fixing
crops (legumes and rice), and the mobilization of N from long-term biological storage
pools. Much of this has occurred in developed nations in which there is intensive use of
industrial fertilizers and large releases of nitrous and nitric oxides into the atmosphere
that ultimately fall to the Earthís surface. There, the rate of fixed N input to the
terrestrial N cycle has increased 5-20 fold (Howarth, R. et al., 1996. Biogeochemistry
35:181-226). The rapid increase in fixed N has greatly outpaced the rate of human
population growth, release of CO2, and deforestation.

The consequences of this substantial human alteration of the global N
cycle include not only the dramatic increase in the worldís agricultural production but
also: increased release of nitrous oxide (N2O), a greenhouse gas; formation of
photochemical smog; losses in other soil nutrients, such as calcium and potassium;
acidification of soils, streams and lakes; increases in the quantity of organic storage in
some ecosystems; loss of biodiversity, especially plants and microbes adapted to efficient
use of nitrogen; and increased transfer of bioavailable N via rivers and the atmosphere to
coastal waters.

The increased loading of N to estuaries, bays and continental shelf
environments has resulted in major changes in these ecosystems, including increased
organic production (eutrophication), algal blooms that decrease water clarity and may
otherwise be harmful, loss of seagrasses and coral reefs due to shading and overgrowth,
depletion or elimination of dissolved oxygen in bottom waters, and losses in fishery
production. Not only have restricted estuaries and lagoons been affected, but ecosystems
of open continental shelf waters that receive substantial riverine inputs from
agricultural or heavily populated regions have been greatly altered since the 1950s. These
include the northwest shelf of the Black Sea, into which the Danube among other rivers
drains, the northern Adriatic Sea, the Baltic and North Seas, and the Gulf of Mexico off
of the Mississippi River. Based on the growing use of industrial fertilizers in the
developing world, particularly south and east Asia, similar problems are anticipated.
Through more efficient application of fertilizers and the restoration of aquatic
ecosystems that serve as a sink for fixed N, returning it to the atmosphere as nonreactive
N2, N loadings to coastal systems can be halved without loss of agricultural production.